Encyclopedic short information about the Jurassic period. Jurassic period
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Jurassic period (Yura) - middle (second) period mesozoic era. It began 201.3 ± 0.2 Ma ago and ended 145.0 Ma ago. It continued in this way for about 56 million years. The complex of deposits (rocks) corresponding to a given age is called Jurassic system. In different regions of the planet, these deposits differ in composition, genesis, and appearance.
For the first time deposits of this period were described in the Jura (mountains in Switzerland and France); hence the name of the period. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates formed in a variety of conditions.
- 1 Jurassic subdivision
- 1.1 Geological events
- 1.2 Climate
- 1.3 Vegetation
- 1.4 Marine organisms
- 1.5 Land animals
- 2 notes
- 3 Literature
- 4 Links
Jurassic subdivision
Jurassic system subdivided into 3 departments and 11 tiers:
| system | Department | tier | Age, million years ago | |
|---|---|---|---|---|
| Chalk | Lower | Berriasian | less | |
| Upper (malm) |
titonian | 145,0-152,1 | ||
| Kimmeridge | 152,1-157,3 | |||
| Oxford | 157,3-163,5 | |||
| Medium (dogger) |
Callovian | 163,5-166,1 | ||
| Bath | 166,1-168,3 | |||
| Bayosian | 168,3-170,3 | |||
| Aalen | 170,3-174,1 | |||
| Lower (lias) |
Toarian | 174,1-182,7 | ||
| Plinsbachsky | 182,7-190,8 | |||
| Sinemursky | 190,8-199,3 | |||
| Goettansky | 199,3-201,3 | |||
| Triassic | Upper | Rhetic | more | |
| Subsections are given in accordance with IUGS as of January 2015 | ||||
Geological events
213-145 million years ago, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.
Climate
The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator).
Vegetation
The drooping cycad (Cycas revoluta) is one of the cycads growing in our timeGinkgo biloba (Ginkgo biloba). Botanical illustration from Siebold and Zuccarini's Flora Japonica, Sectio Prima, 1870
In the Jurassic, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.
Cycads - a class of gymnosperms that prevailed in the green cover of the Earth. Now they are found in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Outwardly, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them among palm trees in his plant system.
During the Jurassic period, groves of gingko trees grew throughout the then temperate zone. Ginkgoes are deciduous (unusually for gymnosperms) trees with an oak-like crown and small, fan-shaped leaves. Only one species has survived to this day - ginkgo biloba.
Very diverse were conifers, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered the temperate zone. The ferns gradually disappeared.
marine organisms
Leedsichthys and liopleurodonCompared with the Triassic, the population of the seabed has changed a lot. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve molluscs fill all the vital niches of the seabed. Many stop collecting food from the ground and move on to pumping water with the help of gills. A new type of reef communities is emerging, approximately the same as it exists now. It is based on six-ray corals that appeared in the Triassic.
land animals
Reconstruction of Archeopteryx,Oxford University Museum
One of the fossil creatures that combine the features of birds and reptiles is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx flew quite badly (planned from tree to tree), and was about the size of a crow. Instead of a beak, he had a pair of toothy, although weak jaws. It had free fingers on its wings (of modern birds, they were preserved only in hoatzin chicks).
In the Jurassic period, small, woolly warm-blooded animals - mammals - live on Earth. They live next to dinosaurs and are almost invisible against their background. In the Jura there was a division of mammals into monotremes, marsupials and placentals.
Dinosaurs (English Dinosauria, from other Greek δεινός - terrible, terrible, dangerous and σαύρα - lizard, lizard), dominated on land, lived in forests, lakes, swamps. The range of differences between them is so great that family ties between their species are established with great difficulty. There were dinosaurs ranging in size from a cat to a whale. Different types of dinosaurs could move on two or four limbs. Among them were both predators and herbivores. Of the latter, the Jurassic period saw the heyday of sauropods - diplodocus, brachiosaurs, apatosaurs, and camarasaurus. Sauropods were hunted by other sauropod dinosaurs, namely large theropods.
Brachiosaurus
Ceratosaurus
pseudotribos
Notes
- International Stratigraphic Scale (version January 2013) on the website of the International Commission on Stratigraphy
Literature
- Jordan N. N. The development of life on earth. - M.: Enlightenment, 1981.
- Karakash N.I.,. Jurassic system and period // encyclopedic Dictionary Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg, 1890-1907.
- Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical Geology: Textbook. - M.: Academy, 2006.
- Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M.: Thought, 1984.
- Yasamanov N.A. Ancient climates of the Earth. - L .: Gidrometeoizdat, 1985.
- Yasamanov N.A. Popular paleogeography. - M.: Thought, 1985.
Links
- Jurassic.ru - A site about the Jurassic period, a large library of paleontological books and articles.
| ← | P A l e O h O th |
Mesozoic (251-65 million years ago) | TO A th n O h O th |
→ | ||
|---|---|---|---|---|---|---|
| ← | Triassic (251-199) |
(199-145) |
Cretaceous period (145-65) |
→ | ||
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Jurassic Information About
And Switzerland. The beginning of the Jurassic period is determined by the radiometric method at 185 ± 5 Ma, the end at 132 ± 5 Ma; the total duration of the period is about 53 million years (according to 1975 data).
The Jurassic system in its modern extent was identified in 1822 by the German scientist A. Humboldt under the name "Jurassic formation" in the mountains of the Jura (Switzerland), the Swabian and Franconian Alb (). In the territory Jurassic deposits were first established by the German geologist L. Buch (1840). The first scheme of their stratigraphy and division was developed by the Russian geologist K.F. Rul'e (1845-49) in the Moscow region.
Subdivisions. All the main subdivisions of the Jurassic system, which were subsequently included in the common stratigraphic scale, are identified in the territory of Central Europe and Great Britain. The division of the Jurassic system into divisions was proposed by L. Buch (1836). The foundations of the stage division of the Jura were laid by the French geologist A. d "Orbigny (1850-52). The German geologist A. Oppel was the first to produce (1856-58) a detailed (zonal) subdivision of the Jurassic deposits. See table.
Most foreign geologists attribute the Callovian stage to the middle section, motivating this by the priority of the three-term division of the Jurassic (black, brown, white) by L. Bukh (1839). The Tithonian stage is distinguished in the sediments of the Mediterranean biogeographic province (Oppel, 1865); for the northern (boreal) province, its equivalent is the Volgian Stage, first identified in the Volga region (Nikitin, 1881).
general characteristics. Jurassic deposits are widespread on the territory of all continents and are present in the periphery, parts of ocean basins, forming the base of their sedimentary layer. By the beginning of the Jurassic period, two large continental masses are separated in the structure of the earth's crust: Laurasia, which included platforms and Paleozoic folded regions of North America and Eurasia, and Gondwana, which united the platforms of the Southern Hemisphere. They were separated by the Mediterranean geosynclinal belt, which was the Tethys oceanic basin. The opposite hemisphere of the Earth was occupied by the Pacific Ocean basin, along the edges of which the geosynclinal regions of the Pacific geosynclinal belt developed.
In the Tethys oceanic basin, during the entire Jurassic period, deep-sea siliceous, clayey, and carbonate deposits accumulated, accompanied in places by manifestations of underwater tholeiite-basalt volcanism. The wide southern passive margin of the Tethys was an area of accumulation of shallow water carbonate deposits. On the northern outskirts, which in different places and in different time had both an active and a passive character, the composition of the deposits is more varied: sandy-argillaceous, carbonate, in places flysch, sometimes with manifestations of calc-alkaline volcanism. The geosynclinal regions of the Pacific belt developed in the regime of active margins. They are dominated by sandy-argillaceous deposits, a lot of siliceous ones, and volcanic activity was very actively manifested. The main part of Laurasia in the Early and Middle Jurassic was land. In the Early Jurassic, marine transgressions from geosynclinal belts captured only territories Western Europe, the northern part of Western Siberia, the eastern margin of the Siberian Platform, and in the Middle Jurassic and southern part East European. At the beginning of the Late Jurassic, the transgression reached its maximum, spreading to the western part of the North American platform, the East European, the entire Western Siberia, Ciscaucasia and Transcaspian. Gondwana remained dry land throughout the Jurassic. Marine transgressions from the southern margin of the Tethys captured only the northeastern part of the African and northwestern part Hindustan platforms. The seas within Laurasia and Gondwana were vast, but shallow epicontinental basins, where thin sandy-argillaceous deposits accumulated, and in the Late Jurassic, in areas adjacent to the Tethys, carbonate and lagoonal (gypsum- and salt-bearing) deposits accumulated. In the rest of the territory, Jurassic deposits are either absent or represented by continental sandy-clayey, often coal-bearing strata that fill individual depressions. The Pacific Ocean in the Jurassic was a typical oceanic basin, where thin carbonate-siliceous sediments and covers of tholeiitic basalts, preserved in the western part of the basin, accumulated. At the end of the Middle - the beginning of the Late Jurassic, the formation of "young" oceans begins; there is an opening of the Central Atlantic, the Somali and North Australian basins of the Indian Ocean, the Amerasian basin of the Arctic Ocean, thereby beginning the process of dismemberment of Laurasia and Gondwana and the separation of modern continents and platforms.
The end of the Jurassic is the time of manifestation of the late Cimmerian phase of Mesozoic folding in geosynclinal belts. In the Mediterranean belt, folding movements manifested themselves in some places at the beginning of the Bajocian, in the pre-Callovian time (Crimea, Caucasus), at the end of the Jurassic (Alps, etc.). But they reached a special scope in the Pacific belt: in the Cordillera of North America (Nevadian folding), and the Verkhoyansk-Chukotka region (Verkhoyansk folding), where they were accompanied by the introduction of large granitoid intrusions, and completed the geosynclinal development of the regions.
The organic world of the Earth in the Jurassic period had a typical Mesozoic appearance. Among marine invertebrates, cephalopods (ammonites, belemnites) reach their peak, bivalves and gastropods, six-pointed corals, "wrong" sea urchins. Among vertebrate animals in the Jurassic period, reptiles (lizards) sharply predominate, which reach giant size(up to 25-30 m) and a great variety. Terrestrial herbivores and carnivores (dinosaurs), sea swimmers (ichthyosaurs, plesiosaurs), flying pangolins (pterosaurs) are known. Fish are widespread in water basins, and the first (toothy) birds appear in the air in the Late Jurassic. Mammals, represented by small, still primitive forms, are not very common. The vegetation cover of the land of the Jurassic period is characterized by the maximum development of gymnosperms (cycads, bennetites, ginkgoes, conifers), as well as ferns.
Jurassic geological period, Jura, Jurassic system, middle period mesozoic. It began 206 million years ago and lasted 64 million years.
For the first time deposits of the Jurassic period were described in the Jura (mountains in Switzerland and France), hence the name of the period. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates formed in a variety of conditions.
190-145 million years ago in Jurassic period the single supercontinent Pangea began to disintegrate into separate continental blocks. Shallow seas formed between them.
Climate
The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator).
In the Jurassic period, vast areas were covered with lush vegetation, primarily a variety of forests. They mainly consisted of ferns and gymnosperms.
cycads- a class of gymnosperms that prevailed in the green cover of the Earth. Now they are found here and there in the tropics and subtropics. Dinosaurs roamed under the canopy of these trees. Outwardly, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them among palm trees in his plant system.
In the Jurassic period, groves of ginkgo trees grew throughout the then temperate zone. Ginkgoes are deciduous (unusually for gymnosperms) trees with an oak-like crown and small, fan-shaped leaves. Only one species has survived to this day - ginkgo biloba. Very diverse were conifers, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered the temperate zone.
marine organisms
Compared with the Triassic, the population of the seabed has changed a lot. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve molluscs fill all the vital niches of the seabed. Many stop collecting food from the ground and move on to pumping water with the help of gills. A new type of reef communities is emerging, approximately the same as it exists now. It is based on six-ray corals that appeared in the Triassic.
land animals
One of the fossil creatures of the Jurassic period, combining the features of birds and reptiles, is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx still flew rather poorly (planned from tree to tree), and was about the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak jaws. It had free fingers on its wings (of modern birds, they were preserved only in hoatzin chicks).
In the Jurassic period, small, woolly warm-blooded animals - mammals - live on Earth. They live next to dinosaurs and are almost invisible against their background.
Dinosaurs of the Jurassic period ("terrible lizards" from Greek) lived in ancient forests, lakes, swamps. The range of differences between them is so great that family ties between them are established with great difficulty. They could be the size of a cat or a chicken, or they could reach the size of huge whales. Some of them moved on four limbs, while others ran on their hind legs. Among them were clever hunters and bloodthirsty predators, but there were also harmless herbivorous animals. The most important feature common to all their species is that they were land animals.
From 213 to 144 million years ago.
By the beginning of the Jurassic period, the giant supercontinent Pangea was in the process of active decay. South of the equator, there was still a single vast mainland, which was again called Gondwana. Later it also split into parts that formed today's Australia, India, Africa and South America. Terrestrial animals of the northern hemisphere could no longer move freely from one continent to another, but they still spread freely throughout the southern supercontinent.
At the beginning of the Jurassic period, the climate throughout the Earth was warm and dry. Then, as heavy rains began to soak the ancient Triassic deserts, the world became greener again, with more lush vegetation. In the Jurassic landscape, horsetails and club mosses grew thickly, which survived from the Triassic period. Palm-shaped bennettites have also been preserved. In addition, there were many griots around. Extensive forests of seed, common and tree ferns, as well as fern-like cycads, spread from water bodies inland. were still common coniferous forests. In addition to ginkgo and araucaria, the ancestors of modern cypresses, pines and mammoth trees grew in them.
Life in the seas.
As Pangea began to split apart, new seas and straits arose, in which new types of animals and algae found refuge. Gradually, fresh sediments accumulated on the seabed. Many invertebrates settled in them, such as sponges and bryozoans (sea mats). in warm and shallow seas other important events took place. There were giant Coral reefs, sheltering numerous ammonites and new varieties of belemnites (old relatives of the current octopuses and squids).
On land, in lakes and rivers, many different types crocodiles, widely dispersed around the globe. There were also saltwater crocodiles with long snouts and sharp teeth for catching fish. Some of their varieties even grew flippers instead of legs to make it easier to swim. Tail fins allowed them to reach greater speed in water than on land. There are also new types sea turtles. Evolution also gave rise to many species of plesiosaurs and ichthyosaurs that competed with new, fast-moving sharks and extremely mobile bony fish.
This cycad is a living fossil. It almost does not differ from its relatives that grew on Earth in the Jurassic period. Now cycads are found only in the tropics. However, 200 million years ago they were much more widespread.
Belemnites, living projectiles.
Belemnites were close relatives of modern cuttlefish and squid. They had internal skeleton cigar-shaped. Its main part, consisting of a calcareous substance, is called the rostrum. At the anterior end of the rostrum there was a cavity with a fragile multi-chambered shell, which helped the animal to stay afloat. This entire skeleton was placed inside the soft body of the animal and served as a solid frame to which its muscles were attached.
The solid rostrum is best preserved in fossil form than any other body part of a belemnite, and it is usually this that falls into the hands of scientists. But sometimes, non-roster fossils are also found. The first such finds at the beginning of the XIX century. baffled many experts. They guessed that they were dealing with the remains of belemnites, but without the accompanying rostrum, these remains looked rather strange. The answer to this mystery turned out to be extremely simple, as soon as more data was collected about the way the ichthyosaurs feed - the main enemies of the belemnites. Apparently, rostless fossils were formed when an ichthyosaur swallowed a whole school of belemnites and regurgitated the soft parts of one of the animals, while its hard internal skeleton remained in the stomach of a predator.
Belemnites, like modern octopuses and squids, developed an inky liquid and used it to create a "smoke screen" when they tried to escape from predators. Scientists have also discovered fossilized belemnite ink sacs (organs in which a supply of ink liquid was stored). One of the scientists of the Victorian era, William Buckland, even managed to extract some of the ink from fossil ink bags, which he used to illustrate his book Bridgewater Treatise.
Plesiosaurs, barrel-shaped marine reptiles with four wide flippers that they rowed through the water like oars.
Glued fake.
No one has yet been able to find a whole fossil belemnite (soft part plus rostrum), although in the 70s. 20th century in Germany, a rather ingenious attempt was made to fool the whole scientific world with a clever forgery. Whole fossils, allegedly taken from a quarry in southern Germany, were purchased by several museums at a very high price, before it was discovered that in all cases the calcareous rostrum was carefully glued to the fossil soft parts of the belemnites!
This famous photograph, taken in 1934 in Scotland, was recently declared a fake. Nevertheless, for fifty years it fueled the enthusiasm of those who considered the Loch Ness monster to be a living plesiosaur.
Mary Anning (1799 - 1847) was only 2 years old when she discovered the first ichthyosaur fossil at Lyme Regis in Dorothy, England. Subsequently, she was lucky to find also the first fossil skeletons of a plesiosaur and a pterosaur.
This child could find
Glasses, pins, nails.
But got in the way
Ichthyosaurus bones.
Born for Speed
The first ichthyosaurs appeared in the Triassic. These reptiles were ideally adapted to life in the shallow seas of the Jurassic period. They had a streamlined body, fins of various sizes and long narrow jaws. The largest of them reached a length of about 8 m, but many species did not exceed a person in size. They were excellent swimmers, feeding mainly on fish, squid and nautiloids. Although ichthyosaurs belonged to reptiles, their fossil remains suggest that they were viviparous, that is, they produced ready-made offspring, like mammals. Perhaps the young ichthyosaurs were born in the open sea, like whales.
Other group predatory reptiles, also widespread in the Jurassic seas, are plesiosaurs. Their long-necked varieties lived near the surface of the sea. Here they hunted for shoals of very large fish with their flexible necks. Short-necked species, the so-called pliosaurs, preferred life at great depths. They ate ammonites and other mollusks. Some large pliosaurs appear to have preyed on smaller plesiosaurs and ichthyosaurs as well.
Ichthyosaurs looked like exact copies dolphins, except for the shape of the tail and an extra pair of fins. For a long time, scientists believed that all fossil ichthyosaurs that fell into their hands had a damaged tail. In the end, they guessed that the spine of these animals had a curved shape and at its end was a vertical tail fin (in contrast to the horizontal fins of dolphins and whales).
Life in the Jurassic air.
In the Jurassic period, the evolution of insects accelerated dramatically, and as a result, the Jurassic landscape eventually filled with endless buzzing and crackling, which were emitted by many new types of insects, crawling and flying everywhere. Among them were predecessors
modern ants, bees, earwigs, flies and wasps. Later, in the Cretaceous period, there was a new evolutionary explosion, when insects began to "make contacts" with the newly appeared flowering plants.
Until that time, real flying animals were found only among insects, although attempts to master air environment observed in other creatures that have learned to plan. Now whole hordes of pterosaurs have risen into the air. These were the first and largest flying vertebrates. Although the first pterosaurs appeared at the end of the Triassic, their true "rise" occurred precisely in the Jurassic period. Light skeletons of pterosaurs consisted of hollow bones. The first pterosaurs had tails and teeth, but in more highly developed individuals, these organs disappeared, which made it possible to significantly reduce their own weight. In some fossil pterosaurs, hair is guessed. Based on this, it can be assumed that they were warm-blooded.
Scientists still disagree about the lifestyle of pterosaurs. For example, it was originally believed that pterosaurs were a kind of "living gliders" that soared like vultures above the ground in the streams of rising hot air. Perhaps they even skimmed over the surface of the ocean, drawn by sea winds, like modern albatrosses. However, now some experts believe that pterosaurs could flap their wings, that is, actively fly, like birds. Perhaps some of them even walked like a bird, while others dragged their bodies along the ground or slept in the nesting places of relatives, hanging upside down, like bats.
Data obtained from the analysis of the fossilized stomachs and dung (coprolites) of ichthyosaurs indicate that their diet consisted mainly of fish and cephalopods(ammonites, nautiloids and squids). The contents of the stomachs of ichthyosaurs made it possible to make an even more curious discovery. Small hard spikes on the tentacles of squid and other cephalopods, apparently, caused a lot of inconvenience to ichthyosaurs, since they were not digested and, accordingly, could not freely pass through them. digestive system. As a result, the spikes accumulated in the stomach, and from them scientists manage to find out what the animal ate throughout its life. So, when studying the stomach of one of the fossil ichthyosaurs, it turned out that he swallowed at least 1500 squids!
How birds learned to fly.
There are two main theories trying to explain how birds learned to fly. One of them claims that the first flights took place from the bottom up. According to this theory, it all began with the fact that bipedal animals, the predecessors of birds, ran and jumped high into the air. Perhaps this is how they tried to escape from predators, or maybe they caught insects. Gradually, the feathered area of the "wings" became large, the jumps, in turn, lengthened. The bird did not touch the ground longer and remained in the air. Add to this the flapping movements of the wings - and it will become clear to you how, after a long time, these "pioneers of aeronautics" learned to stay in flight for a long time, and their wings gradually acquired properties that allowed them to support the body in the air.
However, there is another theory, the opposite, according to which the first flights took place from top to bottom, from trees to the ground. Potential "flyers" had to first climb to a considerable height, and only then throw themselves into the air. In this case, the first step on the way to flying should have been planning, since with this type of movement, energy costs are extremely insignificant - in any case, much less than with the "running-jumping" theory. The animal does not need to make additional efforts, because when planning it is pulled down by the force of the earth's gravity.
The first fossil Archeopteryx was discovered two years after the publication of Charles Darwin's On the Origin of Species. This important discovery was another confirmation of Darwin's theory that evolution is very slow and that one group of animals gives birth to another, undergoing a series of successive transformations. famous scientist and close friend Darwin, Thomas Huxley, predicted the existence of an animal like Archeopteryx in the past, even before its remains fell into the hands of scientists. In fact, Huxley described this animal in detail before it was discovered!
Step flight.
One scientist proposed an extremely curious theory. It describes a series of stages through which the "pioneers of aeronautics" had to pass in the course of the evolutionary process that eventually turned them into flying animals. According to this theory, once one of the groups of small reptiles, called pro-topts, switched to an arboreal way of life. Perhaps the reptiles climbed trees because it was safer there, or easier to get food, or more convenient to hide, sleep, equip nests. It was cooler on the treetops than on the ground, and these reptiles developed warm-bloodedness and feathers for better thermal insulation. Any extra long feathers on the limbs were welcome - they provided additional thermal insulation and increased the surface area of the winged "arms".
In turn, soft, feathered forelimbs softened the impact on the ground when the animal lost balance and fell from tall tree. They slowed down the fall (acting as a parachute), and also provided a more or less soft landing, serving as a natural shock absorber. Over time, these animals began to use feathered limbs as proto-wings. Further transition from para-
from the late stage to the planning stage should have become a completely natural evolutionary step, after which it was the turn of the last, flight, stage, which Archeopteryx almost certainly reached.
"Early" bird
The first birds appeared on Earth towards the end of the Jurassic period. The most ancient of them, Archeopteryx, looked more like a small feathered dinosaur than a bird. She had teeth and a long bony tail adorned with two rows of feathers. Three clawed fingers protruded from each of its wings. Some scientists believe that Archeopteryx used its clawed wings to climb trees, from where it periodically flew back to the ground. Others believe that he lifted himself off the ground using gusts of wind. In the process of evolution, the skeletons of birds became lighter, and the toothy jaws were replaced by a toothless beak. They developed a "wide sternum, to which the powerful muscles necessary for flight were attached. All these changes made it possible to improve the structure of the bird's body, giving it an optimal structure for flight.
The first fossil find of Archeopteryx was a single feather, discovered in 1861. Soon, a whole skeleton of this animal (and with feathers!) was found in the same area. Since then, six fossilized skeletons of Archeopteryx have been discovered, some complete and others only fragmentary. The last such find dates back to 1988.
Age of dinosaurs.
The very first dinosaurs appeared over 200 million years ago. Over the 140 million years of their existence, they have evolved into a wide variety of species. Dinosaurs spread across all continents and adapted to life in a wide variety of habitats, although none of them lived in holes, did not climb trees, did not fly or swim. Some dinosaurs were no bigger than squirrels. Others weighed more than fifteen adult elephants combined. Some waddled heavily on all fours. Others ran faster on two legs than Olympic champions in a sprint.
65 million years ago, all dinosaurs suddenly became extinct. However, before disappearing from the face of our planet, they left us in rocks a detailed "report" of his life and his time.
The most common group of dinosaurs in the Jurassic were the prosauropods. Some of them evolved into the largest land animals of all time - sauropods ("lizards"). These were the "giraffes" of the dinosaur world. They probably spent all their time eating leaves from the tops of trees. To provide life energy such a huge body, an incredible amount of food was required. Their stomachs were capacious digestive containers, continuously processing mountains of plant food.
Later, many varieties of small, swift-footed dinos appeared.
saurs - the so-called hadrosaurs. These were the "gazelles" of the dinosaur world. They plucked the undersized vegetation with their horny beaks and then chewed it up with strong molars.
by the most big family large carnivorous dinosaurs were megalosaurids, or "huge lizards". The Megalosaurid was a ton-weight monster with huge, sharp, saw-toothed teeth that it used to tear through the flesh of its victims. Based on some of the fossilized footprints, his toes were pointing inward. It may have been waddling like a giant duck, swinging its tail from side to side. Megalosaurids populated all areas the globe. Their fossils have been found in places as far apart as North America, Spain and Madagascar.
The early species of this family were, apparently, relatively small animals of a fragile constitution. And later megalosaurids became truly bipedal monsters. Their hind legs ended in three fingers armed with powerful claws. Muscular forelimbs helped in hunting large herbivorous dinosaurs. The sharp claws no doubt left horrific lacerations in the flank of the surprised prey. The powerful muscular neck of the predator allowed him to thrust his dagger-like fangs deep into the body of the prey with terrible force and pull out huge pieces of still warm meat from it.
In the Jurassic period, flocks of allosaurs robbed most of the earth's land. They, apparently, were a nightmarish sight: after all, each member of such a flock weighed more than a ton. Together, allosaurs could easily defeat even a large sauropod.
, conglomerates formed in a variety of conditions.
Jurassic subdivision
The Jurassic system is subdivided into 3 divisions and 11 tiers:
| system | Department | tier | Age, million years ago | |
|---|---|---|---|---|
| Chalk | Lower | Berriasian | less | |
| Yura | Upper (malm) |
titonian | 152,1-145,0 | |
| Kimmeridge | 157,3-152,1 | |||
| Oxford | 163,5-157,3 | |||
| Medium (dogger) |
Callovian | 166,1-163,5 | ||
| Bath | 168,3-166,1 | |||
| Bayosian | 170,3-168,3 | |||
| Aalen | 174,1-170,3 | |||
| Lower (lias) |
Toarian | 182,7-174,1 | ||
| Plinsbachsky | 190,8-182,7 | |||
| Sinemursky | 199,3-190,8 | |||
| Goettansky | 201,3-199,3 | |||
| Triassic | Upper | Rhetic | more | |
| The division is given in accordance with IUGS as of April 2016 | ||||
Geological events
213-145 million years ago, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.
Climate
The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator).
Vegetation
In the Jurassic, vast areas were covered with lush vegetation, primarily a variety of forests. They mainly consisted of ferns and gymnosperms.
land animals
One of the fossil creatures that combine the features of birds and reptiles is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates in Germany. The find was made two years after the publication of Charles Darwin's work " The Origin of Species" and became a strong argument in favor of the theory of evolution - it was initially considered a transitional form from reptiles to birds (in fact, it was a dead-end branch of evolution that was not directly related to real birds) . Archeopteryx flew rather poorly (planned from tree to tree), and was about the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak jaws. It had free fingers on its wings (of modern birds, they were preserved only in hoatzin chicks).
In the Jurassic period, small, woolly warm-blooded animals live on Earth - mammals. They live next to dinosaurs and are almost invisible against their background. In the Jurassic, the division of mammals into monotremes, marsupials, and placentals took place.
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Notes
Literature
- Jordan N. N. development of life on earth. - M .: Enlightenment, 1981.
- Karakash N.I.,. Jurassic system and period // Brockhaus and Efron Encyclopedic Dictionary: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
- Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical Geology: Textbook. - M .: Academy, 2006.
- Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M .: Thought, 1984.
- Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
- Yasamanov N.A. Popular paleogeography. - M .: Thought, 1985.
Links
- - A site about the Jurassic period, a large library of paleontological books and articles.
| ← | P A l e O h O th |
Mesozoic (252.2-66.0 Ma) | TO A th n O h O th |
→ | ||
|---|---|---|---|---|---|---|
| ← | Triassic (252,2-201,3) |
Jurassic period (201,3-145,0) |
Cretaceous period (145,0-66,0) |
→ | ||
An excerpt characterizing the Jurassic period
The trees stood bare and featureless, lazily moving their drooping, thorny branches. Farther behind them stretched a bleak, burnt-out steppe, lost in the distance behind a wall of dirty, gray fog... True, it did not cause the slightest pleasure to make one want to look at it ... The whole landscape evoked horror and longing, seasoned with hopelessness ...- Oh, how scary it is here ... - Stella whispered, shivering. – No matter how many times I come here, I just can’t get used to it... How do these poor things live here?!
- Well, probably, these "poor things" were too guilty once if they ended up here. After all, no one sent them here - they just got what they deserved, right? Still not giving up, I said.
“Now look…” Stella whispered mysteriously.
Before us suddenly appeared a cave overgrown with grayish greenery. And out of it, squinting, stepped out a tall, stately man who in no way fit into this wretched, chilling scenery...
- Hello, Sad! Stella greeted the stranger affectionately. - I brought a friend! She doesn't believe what can be found here good people. And I wanted to show you to her... You don't mind, do you?
- Hello, dear... - the man answered sadly, - Yes, I'm not so good to show me to someone. You are right...
Oddly enough, but this sad man I really liked something right away. He exuded strength and warmth, and it was very pleasant to be near him. In any case, he did not in any way resemble those weak-willed, heartbroken people who surrendered to the mercy of fate with whom this “floor” was packed.
“Tell us your story, sad person…” Stella asked with a light smile.
“Yes, there is nothing to tell there, and there is nothing special to be proud of ...” the stranger shook his head. - And what do you need it for?
For some reason, I felt very sorry for him... Even without knowing anything about him, I was already almost sure that this person could not have done something really bad. Well, I just couldn’t!.. Stella, smiling, followed my thoughts, which she apparently liked very much ...
- Well, okay, I agree - you're right! .. - Seeing her contented face, I finally honestly admitted.
“But you don’t know anything about him yet, and everything is not so simple with him,” Stella said with a sly smile. “Well, please tell her, Sad…”
The man smiled sadly at us, and quietly said:
- I'm here because I killed ... I killed many. But not by desire, but by need, it was ...
I was immediately terribly upset - I killed! .. And I, stupid, believed! .. But for some reason I stubbornly did not have the slightest feeling of rejection or hostility. I obviously liked the person, and no matter how hard I tried, I couldn’t do anything about it ...
“Is it the same fault to kill at will or out of necessity?” I asked. Sometimes people don't have a choice, do they? For example: when they have to defend themselves or protect others. I have always admired heroes – warriors, knights. In general, I have always adored the latter ... Is it possible to compare simple murderers with them?
He looked at me for a long time and sadly, and then also quietly answered:
“I don’t know, dear... The fact that I’m here says that the guilt is the same... But from the way I feel this guilt in my heart, then no... I never wanted to kill, I just I defended my land, I was a hero there... But here it turned out that I was just killing... Is that right? I think no...
So you were a warrior? I asked hopefully. - But then, it's a big difference - you defended your home, your family, your children! And you don't look like a killer!
– Well, we are all different from what others see us... Because they only see what they want to see... or only what we want to show them... As for the war, I also first just as you thought, even proud ... But here it turned out that there was nothing to be proud of. Murder is murder, and it doesn't matter how it happened.
– But this is not right! .. – I was indignant. - What happens then - a maniac-killer turns out to be the same as a hero?! .. This simply cannot be, this should not be!
Everything in me was raging with indignation! And the man sadly looked at me with his sad, gray eyes in which understanding was read ...
“A hero and a murderer take life in the same way. Only, probably, there are “extenuating circumstances”, since a person who protects someone, even if he takes his life, is for a bright and righteous reason. But, one way or another, they both have to pay for it ... And it's very bitter to pay, you believe me ...
- And can I ask you - how long have you lived? I asked, a little embarrassed.
– Oh, quite a long time ago... This is the second time I've been here... For some reason, my two lives were similar - in both I fought for someone... Well, and then I paid... And it's always just as bitter ... - the stranger was silent for a long time, as if not wanting to talk about it anymore, but then he continued quietly. There are people who love to fight. I've always hated it. But for some reason, life brings me back to the same circle for the second time, as if I was locked in this, not allowing me to free myself... When I lived, all our peoples fought among themselves... Some captured foreign lands - others the lands were protected. Sons overthrew their fathers, brothers killed their brothers... Everything happened. Someone accomplished unthinkable feats, someone betrayed someone, and someone turned out to be just a coward. But none of them even suspected how bitter the payment for everything they did in that life would be ...
- Did you have a family there? to change the subject, I asked. - Were there children?
- Certainly! But that was already so long ago!.. They once became great-grandfathers, then died... And some are already living again. That was a long time ago...
– And you are still here?!.. – I whispered, looking around in horror.
I could not even imagine that he had existed here like this for many, many years, suffering and "paying" his guilt, without any hope of leaving this terrifying "floor" even before his hour of return to the physical came. Earth! .. And there he will again have to start all over again, so that after, when his next “physical” life ends, he will return (perhaps right here!) With a whole new “baggage”, good or bad, depending on how he will live his "next" earthly life... And to free himself from this vicious circle (whether it be good or bad) he could not have any hope, since, having begun his earthly life, each person "dooms" himself to this endless, eternal circular "journey"... And, depending on his actions, returning to the "floors" can be very pleasant, or very scary ...
